Principle Skeletal Muscles 1

Muscles of Facial Expression, Muscles that Move the Mandible and Muscles that Move the Eyeballs

Muscles of Facial Expression

The muscles of facial expression provide humans with the ability to express a wide variety of emotions. The muscles themselves lie within the layers of superficial fascia. The origins are generally in the fascia or bones of the skull and insertions into the skin of the face

OccipitofrontalisFront and Occipital Bellies

Front Belly: Origin – Epicranial Aponeurosis Insertion – Skin superior to orbit Action – Draws scalp forward, raises eyebrows

and wrinkles skin of forehead horizontally Occipital Belly

Origin – Occipital and Temporal Bones Insertion – Epicranial Aponeurosis Action – Draws scalp backwards

Orbicularis Oris

Origin – muscle fibers surrounding opening of mouth

Insertion – Skin at corner of mouth Action – Closes and protrudes lips,

compresses lips against teeth and shapes lips during speech

Zygomaticus Major

Origin – zygomatic bone Insertion – Skin at angle of mouth and

orbicularis oris Action – Draws corners of mouth outward

and upward as in smiling

Buccinator

Origin – Maxilla and Mandible

Insertion – Orbicularis Oris Action – presses cheeks

against teeth and lips, as in whistling; draws corner of mouth laterally, assists in chewing be keeping food between teeth

Platysma

Origin – Fascia over deltoid and pectoralis major muscles

Insertion – Mandible, muscles around mouth and skin of lower face

Action – Draws outer part of lower lip downward and backward as in pouting; depresses mandible

Orbicularis Oculi

Origin – Medial wall of orbit Insertion – Circular path around orbit Action – Closes eye; wrinkles forehead

vertically

Levator Palpebrae Superioris

Origin – Roof of Orbit Insertion – Skin of upper eyelid Action - Opens Eye

Muscles that Move the Mandible Also known as muscles of mastication

because they are used for biting and chewing. These muscles also assist in speech.

Masseter

Origin – Maxilla and Zygomatic Arch Insertion – Mandible Action – Elevates and retracts mandible

Temporalis

Origin – Temporal Bone Insertion – Mandible Action – Elevates and retracts mandible

Medial Pterigoid

Origin – Sphenoid bone and maxilla Insertion – Mandible Action – elevates and protracts mandible and

moves mandible from side to side

Lateral Pterygoid

Origin – Sphenoid Bone Insertion – TMJ Action – Protracts mandible, depresses

mandible and moves mandible from side to side

Muscles that Move the Eyeballs Movement of the eyeballs are controlled by

three pairs of extrinsic muscles. These are among the fastest contracting and most precisely controlled skeletal muscles of the body.

Superior Rectus/Inferior Rectus Superior:

Origin – Tendinous ring attached to bony orbit around the optic foramen

Insertion – Superior and central part of the eyeball Action – Moves eyeball upward and medially and rotates its

medially Inferior:

Origin - Tendinous ring attached to bony orbit around the optic foramen

Insertion – Inferior and central part of the eyeball Action – Moves eyeball downward and medially and rotates

it laterally

Lateral/Medial Rectus

Lateral: Origin – Tendinous ring attached to bony orbit

around the optic foramen Insertion – Lateral Side of Eyeball Action – Moves eyeball laterally

Medial: Origin – Tendinous ring attached to bony orbit

around the optic foramen Insertion – Medial Side of Eyeball Action – Moves eyeball medially

Superior/Inferior Oblique

Superior: Origin – Tendinous ring attached to bony orbit around the

optic foramen Insertion – Eyeball between superior and lateral recti Action – moves eyeball downward, laterally and rotates

medially Inferior:

Origin – Maxilla Insertion – eyeball between inferior and lateral recti Action – moves eyeball upward and laterally and rotates it

laterally